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Four processes were needed for the spontaneous origin of life on early Earth: 1. Non-living synthesis of simple organic molecules All of the elements found in organic compounds are thought to have existed on Earth and in the rest of the solar system when the Earth formed. But how and where were these elements assembled into the organic compounds found in life? Read the excerpt from: “Contemporary Work on the Origin of Life” Determine the two locations for which we have evidence of the formation of simple organic monomers. What was early Earth like? (Through the Wormhole video clip #1) About 4.6 billion years ago the planets of our solar system formed by the condensing of matter around our sun The Surface Bombardment by meteorites. Water vapor condensed to liquid, forming oceans. There were frequent lightening / electrical storms The Temperatures were high (little atmosphere to shield heat from the sun) The Atmosphere Earth’s primitive atmosphere formed by volcanic out gassing. The Atmosphere: Then vs. Now THEN: • UV light penetrated Earth’s atmosphere NOW: UV is absorbed by ozone in the atmosphere The Atmosphere: Then vs. Now THEN (?): Consisted of: – – – – – – – Methane Ammonia Water vapor Nitrogen gas Carbon dioxide Hydrogen gas Carbon monoxide Uncertainty remains NOW: Consists of: – Nitrogen gas (N2) – Oxygen gas (O2) The Atmosphere: Then vs. Now THEN (?): Reducing atmosphere: lack of O2 allows formation of complex organic molecules Oparin’s Hypothesis (1923) NOW: Oxidizing atmosphere: free O2 inhibits formation of complex organic molecules Uncertainty Growing evidence suggests that the early atmosphere was made up primarily of nitrogen and carbon dioxide and was neither reducing nor oxidizing. Two testable hypothesized mechanisms for the presence of simple organic molecules on Earth: 1. Organic molecules were created from inorganic matter on Earth 2. Organic molecules were delivered to Earth from outer space Miller and Urey (1953) duplicated Oparin’s early Earth conditions in the lab Methods: In a glass refluxing system, they recreated a miniature oceanatmosphere system They included hydrogen, methane, ammonia and water into the system to model Oparin’s hypothesized pre-biotic atmosphere. The mixture was heated and circulated past an electric spark (to model lightening) before allowing it to condense Amino acids were formed from the inorganic compounds ANIMATION • Other scientists repeated Miller and Urey’s work, eventually producing: – – – – – – Other amino acids ATP Glucose and other sugars Lipids Bases which form RNA and DNA Adenine (the key component of ATP) • These molecules would accumulate over long time periods producing thick, warm "primordial soup“ Conclusion: molecules of life can arise from non-living material TOK: we may be able to show that organic compounds could arise under certain conditions, but we can't determine with certainty whether they did in the past Two testable hypothesized mechanisms for the presence of simple organic molecules on Earth: 1. Organic molecules were created from inorganic matter on Earth 2. Organic molecules were delivered to Earth from outer space Extraterrestrial Hypothesis • Comets contain a variety of organic compounds. • Heavy bombardment 4,000 million years ago may have delivered both organic compounds and water to the early Earth. Example: • Murchison Meteorite • Rich with amino acids • Demonstrates that Earth may have acquired organic compounds from space